This invention relates to improved gaskets, and particularly to improved oil pan gaskets for automotive use.
In a typical environment in which an oil pan gasket of the present invention is adapted to be used, a suitable engine flange at the base of the engine is present. The flange may terminate rearwardly at a retainer, such as a centrally located rear main bearing cap which holds the bearing for the drive shaft. The flange may terminate at the front in a retainer, such as in a timing chamber cover, or at part of the oil pump structure or the like. Most frequently the mating oil pan cover has two generally flat side main flange surfaces which confront the engine flanges and two generally semi-circular recesses at the ends of the cover which receive the bearing cap and other engine component at the front. Thus, to seal in such an environment, the gasket must be generally flat along its side portions and must have end portions which are generally concave to match the generally semi-cylindrical openings in the oil pan.
In the past, frequently four pieces, two generally flat pieces and two generally concave pieces, have been used to seal in this environment, both in original manufacture and in the after-market. When it is appreciated that the gasket must be secured upside-down to the engine (especially during repair), it will be appreciated that such installation is extremely tedious and difficult, and frequently requires additional tube-dispensed sealants to be used as well.
Unitary prior art molded rubber gaskets also exist. Generally they comprise a main body defining bolt or fastener holes and concave ends. These are difficult to install because they are limp. They also suffer from splitting problems at the fastener holes.
Some of the prior art gaskets utilize narrow beads along their lengths around the fastener holes to assist in sealing. Some such gaskets also define additional openings adjacent the fastener holes which receive stops formed with the engine or oil pan to control compression. Other such gaskets simply utilize flat rubber main bodies.
Other prior art molded gaskets for oil pans are generally bead-like in nature. Such gaskets are sometimes used in constructions in which the engine or oil pan defines a recess to receive a bead, like an O-ring or a ring having a cross-section with multiple bead like projections, for sealing in the recess and against the confronting flange. Seals such as this simply cannot realistically be used with flat sealing surfaces, because installation in original manufacture and especially during in-place repair would be virtually impossible.
Because of their difficulties of installation, and because of inherent defects in their sealing characteristics and ability to withstand usual torquing loads, because of variations in engine blocks and fastener holes therein, and for other reasons, oil pan gaskets frequently fail to seal fully and properly. Occasionally this results in higher oil consumption in addition to the failure of an engine. More frequently this results in the familiar oil spots on garage floors and elsewhere. Further, the use of typical oil pan gaskets as described above, such as limp or multi-piece gaskets, makes it virtually impossible for robot installation of the gasket in original manufacture.
Thus, for those and other reasons, an improved oil pan gasket is highly to be desired.
One possible solution to some of the problems would be to provide a molded rubber gasket with a rigid core, such as a metallic core. This would provide sufficient rigidity for a robot to handle and place the gasket appropriately. However in such gaskets, holes are formed therein to accommodate fasteners such as bolts for securing the gasket appropriately relative to the engine and oil pan cover (the zone to be sealed by the gasket). When the fasteners are positioned and tightened, any excess of torquing load tends to split the rubber adjacent to the edge of the core, the gasket then loses its integrity, and the gasket will then tend to fail as an adequate seal. Because the sheet metal sealing flange of the oil pan cover is relatively flexible, the fasteners must be pulled down tightly to maintain the seal therebetween. Thus, even if the torque applied to the fasteners is controlled it is not realistically possible to prevent rubber splitting. Hence the typical molded rubber gasket with a rigid core, such as a metallic core, is not fully suitable as an effective oil pan cover gasket, and the careful control of torquing loads is not a fully effective solution.
It has been determined that the splitting of the rubber is generally in line with the edge of the metal cores commonly used in oil pan gasket environments. It appears that when the gasket is compressed between a pair of flanges to be sealed, the rubber is excessively stressed in multiple directions. Because the rubber does not compress in the sense of being reduced in volume, it becomes displaced. When it is displaced along or towards the edge of a metal core, the core edge may be viewed as acting as a knife edge, tending to cut the rubber which moves relative to it. This weakens the gasket, and produces a weakness in the rubber along the core edge, resulting in the subsequent splitting of the gasket, and its failure.